Telecommunications system with value added service directory and an integrated circuit module therefor

ABSTRACT

In a telecommunications system such as a global mobile telephone network in which each subscriber unit includes a Subscriber Identity Module (SIM card), each SIM card has fixed memory locations (22), to which data can be addressed over the air. Some of the locations (22) can not be overwritten from the subscriber unit but can be accessed therefrom on the entry of short simple codes, each associated with one of the locations. Further fixed memory locations (24) can be read over the air only when the subscriber enters a personal identification number. Locking control files (27, 28) are used to control read/write access to the locations (22, 24) respectively.

This invention relates to a telecommunications system. In particular,but not exclusively, it relates to a mobile communications system suchas a cellular mobile radio or telephone system.

A recent innovation in such systems has been the introduction ofSubscriber Identity Modules (SIM cards). These are integrated circuitcards which can be releasably inserted into a mobile telephone and whichcontain in memory the subscriber's identity, i.e. his telephone number.These known SIM cards also have a rolling buffer which can store acertain number of alphanumeric characters. The buffer facilitates theso-called Short Message Service (SMS) in which a message for asubscriber or for a specified group of subscribers can be broadcast overthe air, as an advanced form of radiopaging. Messages can be received bya mobile telephone whenever it is idle or on stand-by. However, if amessage is received which would overfill the buffer, data is lost on afirst-in-first-out basis.

U.S. Pat. No. 5,127,040 describes a method and apparatus for remotelyloading repertory telephone numbers into a mobile unit. The numbers canbe recalled and used later by the subscriber.

EP-A-0 459 344 describes a method of downloading and executing softwarein a remote terminal of a communications system.

WO-A-91/12698 discloses a mobile radio telephone having a SIM card whichhas been programmed only to authorise the use of certain services. Suchprogramming takes place directly and not remotely.

It is an object of the invention to provide a more efficient andremotely reconfigurable SIM card.

From one aspect, the present invention consists in a telecommunicationssystem comprising at least one host station and a plurality ofsubscriber units, the or each host station being operable to transmit amessage to at least one of the subscriber units, and each subscriberunit having a multiplicity of fixed memory locations and meansresponsive to the detection of the message to store the message in aselected one of the fixed memory locations which can not be overwrittenfrom the subscriber unit, but which can be accessed from the subscriberunit when required, characterised in that each subscriber unit includesmeans responsive to an instruction transmitted from the or each hoststation selectively to enable or prohibit said fixed memory locations tobe overwritten or to be read from the or each host station or from thesubscriber unit.

In this description and the accompanying claims, a "fixed" memorylocations means a location into which data can be written, and excludesfirst-in-first-out or circular buffers. Overwriting of all the data incertain "fixed" memory locations may occur in contrast to thefirst-in-first-out loss of data experienced with current SMS buffers.

Thus, for example, a set of telephone numbers, each with an identifyingalphanumeric tag, can be transmitted to the SIM card, allowing userseasy access to commonly used services such as hotels, car hire orairline reservations. This feature is known as a Value Added ServiceDirectory.

A message may be retrievable by the subscriber on the entry of simple,short codes into the subscriber unit, each memory location correspondingto a particular code. A message may include a telephone number and, oncestored, may be able to be overwritten over the air. Preferably, the oreach host station is operable to transmit a request for informationstored in a subscriber unit. The information may be included in amessage and it may also include information which is stored in a securememory location, accessible only when the subscriber enters a personalidentification number (PIN number). The information may include creditdetails relevant to the subscriber, for example, a credit card number ofcredit status, thus greatly facilitating credit card transactionscarried out over the telephone. Using this feature of the invention, acredit account holder avoids having to dictate his account details andneed only enter the mandatory PIN number.

The host station may be operable to transmit instructions to lock and/orunlock a memory location at the subscriber unit. It may be operable totransmit instructions to run a program stored in memory locations at thesubscriber unit. The host station may be operable to transmit filescontaining functional data and/or files containing non-functional datato the subscriber unit.

The messages, requests for information and the instructions beingtransmitted may be in a specific format which the subscriber unit isable to distinguish from other formats. The specific format may be madesecure against interception.

In a preferred embodiment, the subscriber unit comprises a mobile radioor telephone and an integrated circuit card which can be removablyconnected to the radio-telephone. The integrated circuit card maycontain the memory locations and may contain means for distinguishingthe specific format from other formats. The card may contain means fordistinguishing between the messages, requests for information andinstructions. The card may also contain the means for storing themessages and means for acting on the requests and instructions.

From another aspect, the invention consists in a module for controllinga subscriber unit in a telecommunications system, being removableconnected to a transceiver of the subscriber unit, and comprising amultiplicity of fixed memory locations, and means responsive to thedetection of a message transmitted remotely thereto to store the messagein a selected one of the fixed memory locations, characterised by meansresponsive to instructions transmitted remotely thereto to render any orall of said fixed memory locations accessible or inaccessible foroverwriting or reading from either the subscriber unit or the hoststation.

The module may include a directory structure within which files can bestored.

The invention is particularly applicable to global telecommunicationsystems in which the mobile cellular telephone networks of variouscountries or areas communicate using a common standard. An example ofsuch a global system is GSM (Global System for Mobile Communications)currently operating in Europe. However the invention is not limited toglobal systems and could be applied to a single national cellularnetwork or even to a fixed land-linked network.

An embodiment of the invention will now be described by way of examplewith reference to the accompanying drawings in which:

FIG. 1 shows the transmission of messages to a subscriber unit in asystem according to the invention;

FIG. 2 shows a process in which a subscriber unit transmits a messageand requested information;

FIG. 3 is a block diagram showing elements of a module shown in FIGS. 1and 2;

FIG. 4 shows details of one of the blocks shown in FIG. 3; and

FIG. 5 is a flowchart showing the operation of the module shown in FIGS.1 to 4.

FIG. 1 illustrates an SMS distribution path according to the invention.In the prior art, the short messages have usually been directed to asingle subscriber or a specified group of subscribers such as a salesteam.

However, GSM also supports a feature known as Cell Broadcast in whichmessages can be sent to all the subscribers in a particular area. In theembodiment of the invention illustrated, a message consists of thetelephone number of an advertiser and an alphanumeric tag to identifythe advertiser.

An operator enters the message into a terminal 1. The message is thencoded into a secure format known to applicants as an Embedded CommandStream (ECS) and sent via a modem 2 and a fixed line 3 to a local GSMswitch 4. According to its delivery address, the message is delivered toany or all of the other switches within that network, or even acrossnetworks.

The switch 4, which in this example is in the geographical area to whichthe message is to be transmitted, delivers the message to a number ofcellsites 5. The cellsites 5 are the base transceiver stations of theGSM network.

Each cellsite 5 then broadcasts the message to a group of transceiversor mobile telephones, hereinafter referred to as "mobiles". If CellBroadcast is used, the group consists of all mobiles within thegeographical area at the time of the broadcast.

A selected mobile 6 receiving the message transmits a confirmation ofreceipt back to its respective cellsite 5. From now on, until an updatesituation, the system will not contact this mobile 6 again.

The mobile 6 recognises the message as SMS data and passes it to a SIMcard 7, which is a small self-contained microprocessor, held in a slotin the mobile 6. The SIM card 7 in turn recognises the ECS using specialhardware and software and stores the message in memory in such a waythat it may not be overwritten by the subscriber. Known SIM cardscontain a large number of fixed memory locations in which the subscribercan store frequently dialled numbers and corresponding alphanumerictags. The SIM card 7 of the invention stores the message in one of theselocations, and then carries out a write protect operation. The locationsdedicated to storing write protected messages may be designated by codenumbers relating to a particular category of advertiser. Thus, forexample, car hire company telephone numbers can be stored in location01, hotel reservations in location 02 and so on.

FIG. 2 shows a call placing process in which a subscriber communicateswith an advertiser. The subscriber, remembering that the car hirecompany's number is in location 01 as shown at 8, keys in a short codecorresponding to the location, such as 01#. The mobile 6 theninterrogates the SIM card 7 to retrieve the telephone number from thelocation. The SIM card 7 provides both the number and the alphanumerictag giving the company's name and displays it to the subscriber. Theuser confirms that he wishes to proceed by pressing SEND.

Next, the mobile obtains a voice channel through which the call proceedsto the dialled number. The GSM system automatically handlesintra-network and inter-network hops. At this point the subscriber canhold a voice conversation with the company.

Providing the correct equipment has been installed at the company, assoon as the call is answered, subscriber identity information read fromthe SIM card 7 gives the company immediate customer billing details suchas a name and address.

The SIM card 7 also contains information detailing the subscriber'scredit account. This information is held in a separate, secure memorylocation, accessible only when the subscriber enters a mandatory PINnumber, known only to himself, thus confirming that the mobile has notbeen stolen or lost. When the subscriber has confirmed his car hiredeal, he enters the PIN number into the mobile 6, requesting the creditinformation from the SIM card 7. The SIM card 7 supplies the informationand the mobile uses existing voice/data techniques to transmit theinformation to the company, in a format secure against detection byfraudsters. The sale is confirmed by the company of on its equipment andthe call is terminated.

In this example, it is also possible to obtain a telephone or fax numberfrom the operator-assisted directory enquiries system without thesubscriber having to manually enter the number into the communicationsterminal which he desires to use.

To use this feature, the subscriber calls network directory enquiriesand gives the name of the person, company or service of which he wishesto ascertain the telephone number, as well as any additional informationrequested by the operator answering the call. The operator then locatesthe number, confirms it and enquires as to whether the number is to betransmitted verbally, transferred over SMS into a given memory locationof the subscriber's SIM card or both. If the subscriber chooses a SIMupdate, the voice call is terminated and the operator initiates the SMSprocess by entering a sequence into a computer or pressing a dedicatedbutton. The telephone number is then encoded into an ECS message at thedespatch centre and is posted across the network to the subscriber'scommunications terminal, which transmits a confirmation to the despatchcentre. Thus the retry mechanism, which operates until such aconfirmation is received, is suspended.

The communications terminal recognises the message as SMS data, passesit to the SIM card, and if capable, displays a "message received"banner. The SIM card in turn recognises the ECS using special hardwareand software, and decodes it accordingly. The number, and any associatedalphanumeric tag, which would normally consist of the name of the personor company, are recovered together with the memory location in whichthey are intended to be stored. The number and name-tag are then writtento that location and are write-protected if requested by the subscriber,the overwrite protection being encoded into the message at source.

Subsequently, the subscriber attempts to place a call to the number inthe known memory location by keying in the memory location number. TheSIM card passes the telephone or fax number to the communicationsterminal on demand, and upon receipt of the subscriber's confirmation,the communications terminal sets up the call to the desired number.

FIG. 3 shows the electronic structure of the SIM card 7. The cardcommunicates with the mobile to which it is connected via aninput/output (I/O) manager 15, preferably using the protocol ISO 7816T=0. A filter 16 receives incoming data from the I/O manager and detectsany ECS messages from among the short messages received. The ECSmessages are sent directly to an extended erasable read only memory (E²ROM) 17, which is preferably a "flash" E² ROM. Data can also be outputfrom the E² ROM directly to the I/O manager 15. The remaining blocksshown in FIG. 3 are standard components of a SIM card.

FIG. 4 shows how the E² ROM is organised. A root directory 18 contains aSIM administration and identifier 19, a GSM directory and network data20, and a telecom directory 21.

The telecom directory in turn contains memory locations as follows:"abbreviated dial numbers" 22, "capability configuration" 23, "shortmessages" 24, "fixed dial numbers" 25, and "charging counter" 26. Eachblock represents a plurality of memory locations. The frequently diallednumbers and corresponding alphanumeric tags are stored at locations 22.

The "abbreviated dial numbers" locations 22 and the "short messages"locations 24 each have an associated locking control file 27, 28respectively. The locking control files constitute means for read/writeprotecting and removing read/write protection from their associatedmemory locations. The locking control files 27, 28 will typically be inthe telecom directory 21 as shown, however they can be located elsewheresuch as in an administration directory.

FIG. 5 is a flowchart illustrating the operation of the SIM card 7,which uses the specially fabricated hardware and software which has beendescribed above to implement the operations illustrated. At lozenge 9,messages, requests, and instructions having ECS are distinguished fromthose without. Each of these ECS types consists of a data stream headedby a command which is one of at least four types: write commands for themessages, read commands for the requests for information, attributecommands for lock or unlock instructions and run commands forinstructions to run a program.

The command and data types are decoded at box 10 and acted on in one ofthe four paths 11-14.

Path 11 handles the write commands to store messages starting at alocation specified therein. Path 12 handles the read commands; again,the requests for information contain a location to be accessed first.Successive locations are read and the data stored in a buffer until therequired amount of data has been read. The data in the buffer is thenencoded into the ECS format and despatched from the mobile using SMS tothe calling party.

In path 13, attribute commands are used to lock or unlock specifiedmemory locations and render them accessible or inaccessible, either tocalling parties or to the subscriber. In path 14, run commands cause aprogram stored in the SIM card to be run.

The basic ECS system is expandable to up to 255 internal shell commandsof which write, read, lock/unlock and run are four examples. Thespecific protocol used for the transfer of information is not fixed andcould be ISO7816 T=0 or any other suitable protocol.

The internal shell commands are a supplement to the ability of thesystem to create external file objects within the SIM card 7. The fileobjects are of two types: Application Data File Programs (ADFP's)containing functional data which can be executed by the SIM cardprocessor and can self modify if required and Application Data Files(ADF's) containing non-functional data which does not have thesecapabilities. Existing ADF(P)'s can be modified over-the-air enablingadvanced facilities such as personalisation, re-personalisation ordownloadable phone book.

The SIM card 7 has a directory structure, similar to that of a computerdisk, and new ADF(P)'s can be downloaded into any directory over theair. Also over the air, directories can be created, deleted andmodified, multiple tree directory operations can be carried out andADF(P)'s that are no longer required can be deleted. The amount ofADF(P) data which can be downloaded is limited only by the size of theE² ROM memory of the card.

The invention, as described, greatly extends the applications of SIMcards. For example, using the Value Added Services Directory,subscribers can book hotels and airline seats over their mobiles quicklyand easily.

An additional advantage of this feature of invention is that thegeographical distribution of messages to cards in a specific area suchas the South of France is facilitated. Thus advertisers can direct theirmessages to all mobile subscribers in the specific area. This isparticularly useful when subscribers "roam" from one area to another andhave no knowledge of local services.

The directory enquiries download enables contact telephone or faxnumbers to be delivered to a subscriber's communications terminalwithout any intervention by the subscriber. The process of manuallyentering a number whilst engaged in a call to the operator is oftendangerous, especially when the subscriber is driving.

The ability of the system to download ADF(P)'s means that additionalservices can be added to the SIM card over the air while maintainingtotal compatibility with the existing cellular system. Thus the SIM cardcould acquire the functions of a credit card, passport, driving licence,car park pass, membership card and so on, becoming a multi-service card.Also, dynamically updatable services can be added which require adifferent process to be run each time a service is accessed.

Once the card has extra services on it, it can be used outside of themobile phone environment if desired as a standalone item. This can beread from or written to by a dedicated piece of hardware, such as apoint of sale machine. If desired, the new services can be deleted,however the card will never lose its mobile phone SIM capability. Inaddition, if the card has extra services, they will continue to functioneven if the subscriber has been disconnected from the mobile phonenetwork, unless otherwise desired.

Modifications are possible without departing from the scope of theinvention.

For example, the SIM card can be trained only to receive messagesdetailing services relevant to the subscriber's needs.

We claim:
 1. A telecommunications system comprising at least one hoststation and a plurality of subscriber units, said host station beingoperable to transmit messages to at least one of said subscriber units,and each said subscriber unit having a multiplicity of memory locationsadapted to be accessible from said subscriber unit, means responsive tothe detection of a first message to store said first message in one ofsaid memory locations, access means enabling said memory locations to beselectively accessed from said subscriber unit when required, and meansresponsive to an instruction transmitted from said host stationselectively to enable or prohibit accessing of said memory locationsfrom at least one of said host station and said subscriber unit, atleast one of said subscriber units comprising a transceiver and anintegrated circuit module having said memory locations, and meansresponsive to the detection of said first message by the transceiver toroute said first message to said one of said memory locations, saidmodule being removably connected to said transceiver and including meansresponsive to the entry of a simple short code to read said firstmessage from the respective memory location, means responsive to arequest transmitted from said host station for information stored in aselected one of said memory locations of said module to read andtransmit said information to said transceiver, a multiplicity of furthermemory locations which can be overwritten from the respective subscriberunit, means for selectively enabling or prohibiting said further memorylocations to be overwritten or to be read, means responsive to aninstruction transmitted from said host station for running a programstored in a said further memory location, and means for recognizing aspecific format in which said first message, request for information andinstruction are transmitted.
 2. A telecommunications system comprisingat least one host station and a plurality of subscriber units, each saidsubscriber unit having a multiplicity of memory locations adapted to beaccessible from said subscriber unit, said host station being operableto transmit to at least one of said subscriber units first messagescoded in a predetermined first format and second messages coded in asecond format distinguished from said first format, said second messagescoded in said second format each comprising a data stream including anembedded command which is one of at least a write command for writingdata into a selected said memory location of said subscriber unit, aread command for requesting data stored in said subscriber unit, anattribute command to enable or prohibit access to a selected said memorylocation from at least one of said host station and said subscriberunit, and a run command for executing functional data stored in aselected said memory location, and each said subscriber unit havingmeans for detecting incoming said first and second messages, means fordistinguishing the formats of said first and second messages, meansconnected to said distinguishing means for displaying messagesdistinguished as said first messages, means connected to saiddistinguishing means for decoding messages distinguished as said secondmessages, and means responsive to said commands of said second messagesto determine and undertake appropriate processing of the data containedin said second messages.
 3. A system as claimed in claim 2, wherein eachsaid subscriber unit includes access means enabling said memorylocations thereof to be selectively accessed, when required, to fetchfrom a selected said memory location data stored therein.
 4. A system asclaimed in claim 3, wherein each said subscriber unit includes means topresent information corresponding to data fetched from a selected saidmemory location to a user of said subscriber unit, and means fortransmitting data fetched from a selected said memory location to saidhost station.
 5. A system as claimed in claim 4, wherein said means fortransmitting said data fetched from a selected said memory location isadapted to transmit said data as a second message coded in said secondformat.
 6. A system as claimed in claim 5, wherein said data is fetchedfrom successive said memory locations, is buffered, coded in said secondformat and, thereafter, transmitted.
 7. A system according to claim 3,wherein said memory locations include memory locations identified byshort codes and including means responsive to the entry of a selectedsaid short code by said access means to fetch said data from acorresponding said memory location.
 8. A system as claimed in claim 7,wherein said short codes are abbreviated dial number codes.
 9. A systemas claimed in claim 7, wherein each subscriber unit includes send meansfor instigating dialling of a telephone number contained in said fetcheddata and, in response to an answering signal from said telephone, datais fetched from a predetermined said memory location and sent toreceiving equipment associated with said telephone number.
 10. A systemas claimed in claim 3, wherein said memory locations include securememory locations and said access means is only able to fetch data from aselected said secure memory location in response to entry of a personalidentification signal into said subscriber unit.
 11. A system as claimedin claim 2, wherein said second messages are coded in a secure secondformat.
 12. A system as claimed in claim 11, wherein said first andsecond messages are transmitted using a short message service.
 13. Asystem as claimed in claim 2, wherein said second messages carryexecutable application data file programs for providing each saidsubscriber unit with additional services.
 14. A system as claimed inclaim 2, wherein said memory locations have file handling capabilitiesincluding directory functions.
 15. A system as claimed in claim 14,wherein data involving said attribute commands is stored in lockingcontrol files within predetermined directories.
 16. A system as claimedin claim 2 which is a cellular radio communication system.
 17. A systemas claimed in claim 16, including means for transmitting said secondmessages simultaneously to more than one of said subscriber units viacell broadcasting.
 18. A system as claimed in claim 2, wherein saidmemory locations, detecting and decoding means and means responsive tosaid commands are comprised in integrated circuit modules removablyconnected to said subscriber units.
 19. A module for controlling asubscriber unit in a telecommunications system including at least onehost station, said module being adapted to be removably connected tosaid subscriber unit, and said module comprising a multiplicity ofmemory locations adapted to be accessible from said subscriber unit,means for detecting first and second messages transmitted thereto, saidfirst messages being coded in a predetermined first format and saidsecond messages being coded in a second format distinguished from saidfirst messages used in said system in that said second format comprisesa data stream including an embedded command which is one of at least awrite command for writing data into a selected said memory location, aread command for requesting data stored in said subscriber unit, anattribute command to enable or prohibit access to a selected said memorylocation from at least one of said host station and said subscriberunit, and a run command for executing functional data stored in aselected said memory location, means for detecting incoming said firstand second messages, means for distinguishing the formats of said firstand second messages, means connected to said distinguishing means forinstigating display of messages distinguished as said first messages,means connected to said distinguishing means for decoding messagesdistinguished as said second messages, and means responsive to saidcommands to determine and undertake appropriate processing of datacontained in said second messages.
 20. A module as claimed in claim 19,including means operable to fetch data stored in a selected said memorylocation and transmit said data stored to said subscriber unit.
 21. Amodule as claimed in claim 20, wherein said means responsive to saidcommands is adapted to transmit said data as a second message coded insaid second format.
 22. A module as claimed in claim 20, wherein saidmeans responsive to said commands is also responsive to a personalidentification signal entered into said subscriber unit.
 23. A module asclaimed in claim 20, wherein said memory locations are identified byshort codes and said module includes means responsive to said shortcodes to transmit data from said selected memory location.
 24. A moduleas claimed in claim 19, including a directory structure for addressingsaid memory locations.
 25. A module as claimed in claim 19, wherein saidmodule is programmable for use remotely from said subscriber unit bydownloading extra services onto said module, via said at least one hoststation, prior to removing said module from said subscriber unit.
 26. Amodule as claimed in claim 19, wherein said module is in the form of anintegrated circuit card.
 27. A telecommunications system comprising atleast one host station and a plurality of subscriber units, each saidsubscriber unit having a multiplicity of memory locations adapted to beselectively accessible from said at least one host station and saidsubscriber unit, means at said host station operable to transmit to atleast one of said subscriber units first messages coded in apredetermined first format, means at said host station operable totransmit to said at least one subscriber unit preselected secondmessages coded in a second format which is distinguished from said firstformat, said second format comprising a data stream having an embeddedcommand, and each said subscriber unit having means for receiving saidtransmitted first and second messages, means for distinguishing saidformats, means connected to said distinguishing means for decoding saidsecond messages transmitted in said second format, means for detectingwhen a decoded said second message comprises an embedded command whichis an attribute command selectively identifying at least one of saidmemory locations which is to be locked or unlocked so as to render saidat least one memory location accessible or inaccessible to at least oneof said host station and said subscriber unit, and means for processingsaid attribute command to lock or unlock said at least one memorylocation, whereby to control access to said at least one memory locationfrom at least one of said host station and said subscriber unit.
 28. Asystem as claimed in claim 27, including means for detecting when adecoded said second message comprises an embedded command which is awrite command, and means for writing data comprised in said secondmessage into at least one of said memory locations.
 29. A system asclaimed in claim 28, wherein said attribute command locks said at leastone memory location to prevent overwriting from at least one of saidhost station and said subscriber unit.
 30. A system as claimed in claim29, wherein each said subscriber unit includes access means enablingsaid memory locations of said subscriber unit to be selectivelyaccessed, when required, to fetch from a selected said memory locationdata stored therein.
 31. A system as claimed in claim 30, wherein eachsaid subscriber unit includes means to present information correspondingto data fetched from a selected said memory location to a user of saidsubscriber unit, and means for transmitting data fetched from a selectedsaid memory location to said at least one host station.
 32. A system asclaimed in claim 27, wherein said attribute command locks said at leastone memory location to prevent reading of data stored therein from atleast one of said host station and said subscriber unit.
 33. A system asclaimed in claim 27, including means for detecting when said decodedsecond message comprises an embedded command which is a read command,and means for reading data stored in at least one of said memorylocations as identified by said read command, a buffer for storing thedata read from said at least one memory location, means for encodingsaid stored data into a third message coded in said second format, andmeans for transmitting said third message.
 34. A system as claimed inclaim 33, wherein said at least one memory location is a secure memorylocation and said data is only fetched and transmitted from a saidsecure memory location in response to entry of a personal identificationsignal into said subscriber unit.
 35. A system as claimed in claim 27,including means for detecting when a decoded said second messagecomprises an embedded command which is an execute command, and means forexecuting data stored in at least one said memory location.
 36. A systemas claimed in claim 27, including means for detecting when a decodedsaid second message comprises an executable application data fileprogram for providing additional services, and means for executing saidprogram.
 37. A module for controlling a subscriber unit in atelecommunications system including at least one host station, saidmodule being adapted to be removably connected to said subscriber unit,and said module comprising a multiplicity of memory locations adapted tobe selectively accessible from said at least one host station and saidsubscriber unit, means for detecting first and second messagestransmitted thereto from said at least one host station, said firstmessage being coded in a predetermined first format and said secondmessage being coded in a second format which is distinguished from saidfirst format, said second format comprising a data stream having anembedded command, said module further comprising means for detectingreceived first and second messages, means for distinguishing saidformats, means connected to said distinguishing means for decoding saidsecond messages coded in said second format, means for detecting when adecoded said second message comprises an attribute command selectivelyidentifying at least one of said memory locations which is to be lockedor unlocked so as to render said at least one memory location accessibleor inaccessible to at least one of said host station and subscriberunit, and means for processing said attribute command to lock or unlocksaid at least one memory location, whereby to control access to said atleast one memory location from at least one of said host station andsaid subscriber unit.
 38. A module as claimed in claim 37, includingmeans for detecting when a decoded said second message comprises anembedded command which is a write command, and means for writing datacomprised in said second message into at least one of said memorylocations.
 39. A module as claimed in claim 38, wherein said attributecommand locks said at least one memory location to prevent overwritingfrom at least one of said host station and said subscriber unit.
 40. Amodule as claimed in claim 39, wherein each said subscriber unitincludes access means enabling said memory locations of said subscriberunit to be selectively accessed, when required, to fetch from a selectedsaid memory location data stored therein.
 41. A module as claimed inclaim 40, wherein each said subscriber unit includes means to presentinformation corresponding to data fetched from a selected said memorylocation to a user of said subscriber unit, and means for transmittingdata fetched from a selected said memory location to said at least onehost station.
 42. A module as claimed in claim 37, wherein saidattribute command locks said at least one memory location to preventreading of data stored therein from at least one of said host stationand said subscriber unit.
 43. A module as claimed in claim 37, includingmeans for detecting when said decoded second message comprises anembedded command which is a read command, and means for reading datastored in at least one of said memory locations as identified by saidread command, a buffer for storing the data read from said at least onememory location, means for encoding said stored data into a thirdmessage coded in said second format, and means for transmitting saidthird message.
 44. A module as claimed in claim 43, wherein said atleast one memory location is a secure memory location and said data isonly fetched and transmitted from a said secure memory location inresponse to entry of a personal identification signal into saidsubscriber unit.
 45. A module as claimed in claim 37, including meansfor detecting when a decoded said second message comprises an embeddedcommand which is an execute command, and means for executing data storedin at least one said memory location.
 46. A module as claimed in claim37, including means for detecting when a decoded said second messagecomprises an executable application data file program for providingadditional services, and means for executing said program.